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cutting into existing cast iron sewer pipe

02-08-2007, 03:11 PM

I read the other thread by a similar name, didn't totally answer my question. Here goes .. I have a ~100yr old house with a cast iron main stack (4"). I'm adding a bathroom toilet/sink and need to tap into it. New stuff will be PVC (yes, I know about venting requirements, etc). 1) typical approach is to buy a saddle whereby you remove a 6" section or so. I don't really want to do that for several reasons -- chief among them not wanting to support 45 feet (3 10' floors, plus basement, plus roof part) of it when I do. 2) I'd prefer to cut an angled hole in it to allow the 3" PVC to enter at a 30 degree angle (that'd be an oblong hole). I'd cut the PVC accordingly so as not to introduce sharp edges inside the older pipe (thus providing a clog spot). 3) Seems the easiest way to cut a precise hole like this would be a plasma torch, although I've never tried using one on cast iron (works on 1/2" mild steel just fine though). I'm also concerned about intentionally introducing fire into a pipe which might contain methane. Should I haul a Co2 (or anything inert and heavier than air) tank up to the roof and backfill the pipe with gas to avoid a problem? Before I go buy a plasma torch ($1400) and test my theory, can someone tell me if I'm up the wrong creek here?

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Freddy has the right idea. Before you get totally over your head in a huge mess, call in a good plumbing contractor. It might end up being best to pretty much replace the cast iron stack and use (check codes) a special Y fitting for the vent. Some of the cast iron might be best left in place. This is where you really do want to call in a good plumber. He will know about special fittings, code requirements and such. If you DIY and end up with a mess, you'll end up paying more $$$ to have it all removed and done over.

By the way do be careful of flamable gases in any sewer line.

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I'm also going to agree with Woussko and Freddy. Please don't take a plasma tourch to the main stack. Those old stacks use lead and oakum to seal there joints which is an art all on its own. Just save your self a lot of head aches and lot cheaper in the long run. Call a plumber.

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Why can't folks answer the original question? If I wanted to call a plumber, I'd have used the yellowpages and not asked an "experts" forum. I don't want to install one of those rubber saddle things if I can avoid it .. but if I could cut the existing pipe and install a new cast-iron "Y", I'd do that, then tie into it with plastic. Is doing that possible when you can't create "extra" vertical clearance for the purpose of installing the fitting? Also .. when cutting the pipe, you'd end up with 2 "clean" ends (sans the bell fitting) .. how is that accomodated? For the record .. future suggestions of "call a plumber" are of no help.

Why can't folks answer the original question? If I wanted to call a plumber, I'd have used the yellowpages and not asked an "experts" forum. I don't want to install one of those rubber saddle things if I can avoid it .. but if I could cut the existing pipe and install a new cast-iron "Y", I'd do that, then tie into it with plastic. Is doing that possible when you can't create "extra" vertical clearance for the purpose of installing the fitting? Also .. when cutting the pipe, you'd end up with 2 "clean" ends (sans the bell fitting) .. how is that accomodated? For the record .. future suggestions of "call a plumber" are of no help.

mindcandy, i will answer your question, but have to agree with everyone that posted their answer of hiring a plumber.

the fittings we use now are cast iron. they are refered to as "no hub" they install with stainless steel and rubber no hub couplings. the exisiting pipe is cut approx. 1/2'' larger than the fitting. in your case use a 4.5'' grinder with a cut off blade. no plasma cutter! then the bands can be rolled, folded over to allow for slipping in and folding back into position. then the bands are torqued to 60 inch pounds, approx = to as tight as you can make it with a 5/16'' nut driver by hand.

i kow you want to do it yourself and save some money, but you need to know the basics of right and wrong. your statements were way wrong. that's why all said to hire a plumber. see if a plumber can work with you and therefore you can learn some of the basics for a do it yourself job.
a plasma cutter is a great tool. just not on this application.

rick.

welcome and if you actually stick around this forum, you will see that most are here to help you and others. you just asked too scary of a statement. stick around and you can learn alot from all of us.
rick.

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I'm just curious as to whether you've already contacted a plumber to get a quote on this?

I mean... $1400 for a tool that you only need for this seems a bit steep just to learn how to do something yourself that might potentially blow up your house.

I'm sort of in your shoes. I want to attempt everything myself so I can learn and feel like I've accomplished something beyond just fixing the problem. The pros in this forum have been quite helpful to me so far in this respect, but you have to know where to draw the line. It sounds to me like this isn't even going to be something you're learning that's going to be useful to you going forward, since you're highly unlikely to come across this sort of thing again.

Would it really be that hard to replace the whole thing with PVC? That's just a shot in the dark... I don't even really know what you're talking about.

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Yes, it would be hard to replace the whole thing with PVC, as this is the last floor (the first one) of a whole-house tear-out and remodel (note to the nay-sayers .. I've quite successfully done all the other plumbing work, replacing all the galvanized with copper, etc.). The rest of the cast iron is buried behind already-finished drywall.
After researching the various fittings and reading other suggestions, it seems that the rubber/stainless &quot;slip-over&quot; adapters are the way to go. I do have enough clearance to use a snap cutter, so I'll probably go that route once I figure out how to effectively support the weight above.

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you shouldn't try a snap cutter on 100 year old pipe unless you have plenty of extra pipe incase it crushes. a 4.5'' grinder with a cut off blade will work great with no chance of breaking. just watch the sparks.

you can buy a riser clamp 4'' and temporary install it on the roof or support it in the attic with the clamp and some 2x4.

if you've done this much plumbing so far, you should really be more exposed to how this is done. get a little bit of help so you can learn right from wrong and not damage your house or youself.

rick.

phoebe it is

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Thanks .. a 4 1/2" grinder is only $170 (plus a bunch of wheels) .. that's a better deal. Also looks like Fernco sells the couplings online to "regular folk" (if not, I'll order through work anyway), and I can get pipe and other parts from another online vendor.

I know you "pros" probably hate it, but the Internet is great when it comes to this specialty stuff .. with one click, we can get the parts that would otherwise require a trip to the supply house (where we'd be unlikely to get any help at all as a non-business customer).

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Well Bud I wasn't trying to be rude just truthful, A plasma cutter won't cut cast iron pipe there is to high of a carbon content and it will just make a hole lot of sparks. If you really want to atempt this, ( I still think you should call someone) this is how, Figure out where all your fixtures are that you want (just put in a lav and a toilet) Mesure how far you are away from the stack you are. The trap arm of your toilet can be a max of 3m with a vertical drop of know more than 1m. Conect this to the soil stack with a 3x3 y and a 45(Make sure you suport your stack above and below where you cut the stack to put in the new y(a riser clap works well for this). Some ware on the 3" trap arm put a 3x1 1/2" y and go to your lav (make sure you don't exceed 1 pipe dia in grade (using a 1/4" per ft)) and you want to vent your lav with a 1 1/2 half and tie back into the stack above all other fixtures or open air (through the roof).You now have a toilet that is wet vented through your lav. It sounds easy and it is if you know what your doing. Make sure you ware proper ppe and of course have fun.
Tyler

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I'm also going to agree with Woussko and Freddy. Please don't take a plasma tourch to the main stack. Those old stacks use lead and oakum to seal there joints which is an art all on its own. Just save your self a lot of head aches and lot cheaper in the long run. Call a plumber.